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Discussion Starter · #1 ·
I know this is the E46 forum - but I thought I would post here in case it is useful to anyone else.
I upgrade the E46 to a 2010 E92 2 years ago. Only 40K miles. The car had a check engine light on, and I pulled the code and diagnosed a bad coil, replaced all plugs and coils due to age - and reset the DME. Car ran fine. Took it to smog and they could not run smog check in CA because the emissions readiness monitors were "not ready" - the guy told me to drive it some more. Did another 200 miles.Took it back to the test station - still not ready - in particular the CAT and O2 monitors. Drove another 1000 miles, then I plugged in my Foxwell reader - ran live data tests on the O2 sensors - both pre and post cat - they both seemed to track voltage up/down as you revved the engine, and lifted off. I searched the forums and someone said run. a bottle of CATACLEAN through the system, which I did. I plugged in the ODB reader again, and this time got CCM Ready and N/A on all of the other systems - but at least no "Not ready or INC (incomplete). Took it back to the smog station - he plugged in his reader - said O2 and CAT was still "not ready" and suggested I go to the BMW dealer as they are the only ones who can refresh the ECU and force a reset. Hmm.... I went to the dealer, they wanted $400 just to run diagnostics. And then who knows what parts they would have replaced ! Plus the "smog expert" guy was not available that day. OK, I decided to see what happened if I pulled the battery cable - it is a pain in the butt to access that cable in the trunk ! Left it disconneced for a coupe of mins, and then plugged in reader again - OK - now it was showning some of the monitors ready and some not ready including EVAP, O2, CAT. I decided to do the "drive" cycle on the 405 - idle from "cool" for 3 mins - then drive to freeway - keep a steady 55 mph for a few miles - slow down to 20mph - accelerate slowly back up to 55mph. That is a dangerous procedure on the 405 at 11am. ! Anyway, I had the ODB plugged in - and saw the all of the monitors start to set as "ready" or (OK) - except for EVAP (took about 10 miles and 15 mins of driving slow). Drove back to the smog station - he plugged in his reader - and said "what did you do" ? Everything was ready - including EVAP by the time I got back to the Smog Station. Passed the retest for $10. WooHoo. I told him I pulled the battery rather than just doing a soft reset on the DME - and the tech who had. a lot of BMW customers told me "wow that is a new one - I learned something" ... hope this can help some of you other guys that are running into similar issues.
 

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Discussion Starter · #2 ·
I just posted about me California smog experience .. quick summary is that resetting codes with the reader may not be sufficient . I ended up having to unplug the battery to hard reset the dme ... then I was able to complete the drive cycle In 10 miles at 55mph plus 3 mins idle before that ... o2 and cat monitors that had not reset in 2000 miles of driving reset in 15 mins ...
 

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E30M3 Race F10 535 R1150Rt M Coupe
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summary is that resetting codes with the reader

This makes not much sense to me. But then again I use factory don't diagnostic/ programing tools. What was it you used?
 

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See my recent post on smog .... pull battery to hard reset dme .. then drive cycle .. worked in 10 miles ! Of course ymmv...

1.) It is not necessary to "hard reset". The car has had the check engine light (ECU) reset, and this puts it into monitor mode. The monitors do not come to ready.
2.) This post is from nine years ago. I'm pretty sure the car has smogged by now.
 

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E30M3 Race F10 535 R1150Rt M Coupe
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I've been trained by Bosch and BMW.
Can someone explain to me what a hard reset (presumably there's a soft?) is?

It's never come up in any training nor any diagnostic or training document.
 

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My guess is the controller got itself into some state where a soft reset from the code reader was not enough to get the monitors to run/set ... hard power cycle is sometimes required for even the best embedded systems
No, that is not what happened. The emissions monitor data is stored in flash, not in RAM, so a battery reset does nothing for them.
It was a coincidence that it completed the drive cycle after that.
 

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I've been trained by Bosch and BMW.
Can someone explain to me what a hard reset (presumably there's a soft?) is?

It's never come up in any training nor any diagnostic or training document.
There is no such thing. OP is spewing incorrect info in various old threads.
His emissions monitors passed by coincidence after a battery reset.
 

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Discussion Starter · #12 ·
Well, I beg to differ. There are quite a few threads about this isssue. my original post got sent to the e90 forum .. so I made a note in one of the old posts here, just in case it helps others. I don’t think it’s is a coincidence that after driving 2000 miles to try and reset the monitors that they reset in 10-20 miles after pulling the battery. You are correct sir that the values are held in non volatile memory .. but if the code that runs on the ecu to set the values gets corrupted in ram ... then that could explain why things cannot be reset just by issuing a dme reset from the odb2 port. How does ram get corrupted ? Alpha particle is most common mechanism. I’ve even seen this in flash memory controllers - where it’s not the flash that you have to worry about, since that can be error corrrected on read , but the sram than that can bit flip and cause issues. Rare but possible. Ok, I’m not saying that is 100% for sure what happened here .. only that this might be something quick and easy for others to try if they have a similar issue.
 
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